Item1823: Using FastCGIEngineContrib together with CODE_ENSCRIPT results in an error when viewing the topic

Configure the system to use FastCGIEngineContrib with mod_fcgi or mod_fastcgi. Create a test topic with this content:

%CODE_ENSCRIPT{ lang="bash" }% #!/bin/bash
%ENDCODE%

When trying to view this topic the following error shows up in the browser window::

Foswiki detected an internal error - please check your Foswiki logs and webserver logs for more information.

Can't locate object method "FILENO" via package "FCGI::Stream"

and in apache error log:

[Fri Jul 10 18:31:40 2009] [warn] mod_fcgid: stderr: Can't locate object method "FILENO" via package "FCGI::Stream" at /usr/share/perl5/IPC/Run.pm line 1118.

Encountered on Debian Lenny with apache2.

-- IngoKappler - 10 Jul 2009

Thanks for the bug report. Hopefully I will have time at the weekend to set up a Fast CGI environment and take a look.

Perhaps if I can remove the dependency on IPC::Run (Item8077) then this will no longer be an issue.

-- AndrewJones - 13 Jul 2009

I cannot reproduce this in my environment. What version of IPC::Run are you using? I am using 0.80.

-- AndrewJones - 07 Aug 2009

On my Debian is this installed: libipc-run-perl 0.80-2. There are also some other package named libipc-XXXXX-perl which are all not installed on my system.

I just retested and could still reproduce the issue:

Could it be helpful to look at the related apache-foswiki configuration? I could make it available to you.

-- IngoKappler - 07 Aug 2009

I get the same error when using BDB under FCGI. Here's a link that says that this is an FCGI problem (patch included): http://www.mail-archive.com/ports%40openbsd.org/msg16948.html

--- /usr/lib/perl5/FCGI.pm.orig 2009-08-11 19:16:38.000000000 +0200
+++ /usr/lib/perl5/FCGI.pm      2009-08-11 19:16:41.000000000 +0200
@@ -134,7 +134,7 @@
 # Apparently some use fileno to determine if a filehandle is open,
 # so we might want to return a defined, but meaningless value.
 # An alternative would be to return the fcgi stream fd.
-# sub FILENO { -2 }
+sub FILENO { -2 }

 1;

-- MichaelDaum - 11 Aug 2009

Here's a patch that monkey patches FCGI::Stream via FastCGIEngineContrib:

--- lib/Foswiki/Engine/FastCGI.pm       (revision 4640)
+++ lib/Foswiki/Engine/FastCGI.pm       (working copy)
@@ -56,6 +56,13 @@
 *VERSION = \$Foswiki::Contrib::FastCGIEngineContrib::VERSION;
 *RELEASE = \$Foswiki::Contrib::FastCGIEngineContrib::RELEASE;

+# hack for perl libraries that use FILENO, alternatively patch FCGI.pm
+BEGIN {
+  sub FILENO { -2 }
+  *FCGI::Stream::FILENO = \&FILENO;
+}
+
+
 our $hupRecieved = 0;

Gilmar, do you think this is worth adding to FastCGIEngineContrib?

-- MichaelDaum - 11 Aug 2009

Reading FCGI code, I think that a semantically correct solution would be (untested):

BEGIN {
    *FCGI::Stream::FILENO = sub {
        my ($stream) = @_;
        return fileno ${ $stream->{in} } if $stream->{type} == FCGI::FCGI_STDIN;
        return fileno ${ $stream->{out} }
          if $stream->{type} == FCGI::FCGI_STDOUT;
        return fileno ${ $stream->{err} }
          if $stream->{type} == FCGI::FCGI_STDERR;
    };
}

But maybe this would cause more problems than it'd solve things... I think it needs careful tests to map side effects. The goal is: if a code calls fileno to figure out if the handle is open, any meaningless defined value is enough. But if the intention is to read/write to the handle directly (or to build another handle with dup), then it needs special attention. I don't know how Perl deals with this situation and it's what need to be tested.

-- GilmarSantosJr - 14 Aug 2009

This gets more and more important as the only reasonable Foswiki PageCache backend is BDB... which only works if we solve FILENO in FCGI.

-- MichaelDaum - 21 Aug 2009

I want to see more cases where FILENO is required... but it's interesting to add the first workaround suggested to get things working.

How can I reproduce the issue with BDB?

-- GilmarSantosJr - 23 Aug 2009

Go to configure, enable the PageCache and enable the BDB backend.

-- MichaelDaum - 24 Aug 2009

It seems newer fcgi now does implement a FILENO. So hacking it in via FastCGIEngineContrib isnt necessary anymore. Infact, I get a "redefined" error with above patch.

-- MichaelDaum - 06 Jul 2010